With framework version 6.35 (also included in installer 6.35), we modified the type of the U_SipVersion column in the modules table in the coresuite database (for HANA Standard, HANA onDemand and SQL onDemand: SWA_MODULES in the company database).
Due to this change, a framework downgrade to a framework version lower than 6.35 is no longer possible in the common manner.
While it is theoretically still possible, we do not recommend it. Should you feel you require to perform any framework downgrade to any version lower than 6.35, please contact Support.
Please note, that any downgrades are only ever performed at your own discretion in the first place.
Once you are using at least framework version 6.41, you can again perform any framework version downgrade to max. framework version 6.35 as you had been accustomed to in the past.